Category:NRC Information Notice[Table view]The following query condition could not be considered due to this wiki's restrictions on query size or depth: <code> [[:Beaver Valley]] OR [[:Millstone]] OR [[:Hatch]] OR [[:Monticello]] OR [[:Calvert Cliffs]] OR [[:Dresden]] OR [[:Davis Besse]] OR [[:Peach Bottom]] OR [[:Browns Ferry]] OR [[:Salem]] OR [[:Oconee]] OR [[:Mcguire]] OR [[:Nine Mile Point]] OR [[:Palisades]] OR [[:Palo Verde]] OR [[:Perry]] OR [[:Indian Point]] OR [[:Fermi]] OR [[:Kewaunee]] OR [[:Catawba]] OR [[:Harris]] OR [[:Wolf Creek]] OR [[:Saint Lucie]] OR [[:Point Beach]] OR [[:Oyster Creek]] OR [[:Watts Bar]] OR [[:Hope Creek]] OR [[:Grand Gulf]] OR [[:Cooper]] OR [[:Sequoyah]] OR [[:Byron]] OR [[:Pilgrim]] OR [[:Arkansas Nuclear]] OR [[:Braidwood]] OR [[:Susquehanna]] OR [[:Summer]] OR [[:Prairie Island]] OR [[:Columbia]] OR [[:Seabrook]] OR [[:Brunswick]] OR [[:Surry]] OR [[:Limerick]] OR [[:North Anna]] OR [[:Turkey Point]] OR [[:River Bend]] OR [[:Vermont Yankee]] OR [[:Crystal River]] OR [[:Haddam Neck]] OR [[:Ginna]] OR [[:Diablo Canyon]] OR [[:Callaway]] OR [[:Vogtle]] OR [[:Waterford]] OR [[:Duane Arnold]] OR [[:Farley]] OR [[:Robinson]] OR [[:Clinton]] OR [[:South Texas]] OR [[:San Onofre]] OR [[:Cook]] OR [[:Comanche Peak]] OR [[:Yankee Rowe]] OR [[:Maine Yankee]] OR [[:Quad Cities]] OR [[:Humboldt Bay]] OR [[:La Crosse]] OR [[:Big Rock Point]] OR [[:Rancho Seco]] OR [[:Zion]] OR [[:Midland]] OR [[:Bellefonte]] OR [[:Fort Calhoun]] OR [[:FitzPatrick]] OR [[:McGuire]] OR [[:LaSalle]] OR [[:05000000]] OR [[:Zimmer]] OR [[:Fort Saint Vrain]] OR [[:Shoreham]] OR [[:Satsop]] OR [[:Trojan]] OR [[:Atlantic Nuclear Power Plant]] OR [[:Skagit]] OR [[:Marble Hill]] OR [[:Crane]] </code>.
The explosion resulted from a phase-to-phase short
in a cable bundle in the potential transformer (PT) fuse compartment.
The electrical control cabinet was supplied by Power Systems Division of
General Motors, the diesel generator manufacturer.
The licensee's investiga- tion revealed that the cables routing power from the PT fuses to the trans- formers shorted after their insulation failed because of an overtemperature
condition.
This condition is believed to have been caused by an excessive
air gap and/or poor contact between the spring finger contact arrangement
The spring finger contacts were manufactured by Allis-Chalmers.
The moveable contacts are mounted to the PT fuse compartment door so that when
the door is opened, the contacts disconnect, thereby preventing anyone from
pulling the fuse while it is carrying current. When the door is closed, the
moveable contact finger connects with the stationary contact. Although the
contacts were destroyed by the event, the licensee concluded that an air gap
due to misalignment or contact degradation from corrosion, pitting, or burning, caused arcing and eventual failure. Although the cause has been attributed to
inadequate maintenance of the contact, the licensee is considering design changes
The licensee inspected the other seven diesel generator control cabinets and
found three other instances of poor contact.
Visual inspection for burning, pitting, corrosion and proper alignment and mating of contact surfaces were
performed as well as micro-ohmmeter checks.
Since 1973, four previous onsite
events involving this type of pressure contact arrangement have occurred on
non-safety-related electrical boards designed by General Electric Co.
Because
of this type of problem, General Electric modified similar contacts on its
electrical boards to knife switch contacts.
The licensee considers the problem
to be generic and has initiated a visual inspection of all PT fuse compart- ments.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the Regional
Administrator of the appropriate regional office or this office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
C. Brooks, RII
(205) 729-6196
Samuel D. MacKay, NRR
(301) 492-8394 Attachment:
List of Recently Issued NRC Information Notices
f*SEE PREVIOUS CONCURRENCES
RII
OGCB:DOEA:NRR
CBrooks
SDMacKay
p8hX87 08/11/87
_BY ?"Ao
IS7,s'-*eR
PPMB:ARM
TechEd
08/12/87
C/OGCB:DOEA:NRR
CHBerlinger
08/27/87
08/-//87
IN 87-XX
August, 1987 Discussion:
The licensee Inspected the other seven diesel generator control cabinets and
found three other Instances of poor contact. Visual Inspection for burning, pitting, corrosion and proper alignment and mating of contact surfaces were
performed as well as micro-ohmmeter checks. Since 1973, four previous onsite
events involving this type of pressure contact arrangement have occurred on
non-safety-related electrical boards designed by General Electric Co.
Because
of this type of problem, General Electric modified similar contacts on its
electrical boards to knife switch contacts. The licensee considers the problem
to be generic and has initiated a visual inspection of all PT fuse compart- ments.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the Regional
Administrator of the appropriate regional office or this office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
C. Brooks, RU1
(205) 729-6196
Samuel D. MacKay, NRR
(301) 492-8394 Attachment:
List of Recently Issued NRC Information Notices
SEE PREVIOUS CONCURRENCES
RII
OGCB:DO EA:NRR
CBrooks
SDMacKay
08/ /87 08/11/87
PPMB:ARM
TechEd
08/12/87 C/OGCB: DOEA:NRR
CHBerlinger
08/ J/87 D/DOEA:NRR
CERossi
08/ /87
IN 87-XX
August, 1987 Discussion:
The licensee inspected the other seven diesel generator control cabinets and
found three other instances of poor contact.
Visual inspection for burning, pitting, and corrosion and proper alignment and mating of contact surfaces were
performed as well as mlcrohmmeter checks.
Four previous onsite events involv- ing this type of pressure contact arrangement have occurred dating back to 1973 on non-safety related electrical boards.